The present invention relates to the field of geophysical seismic data collection. More particularly, the present invention relates to an integrated system for collecting, storing and processing seismic and navigation data from an exploration prospect, and for enhancing quality control of such data.
Marine seismic exploration investigates the geophysical structure of formations underlying water. A seismic source array is towed by a vessel through the water, and a sensor array detects signals generated by wave reflections from subsurface geologic formations. The seismic source array utilizes air guns or other multiple wave generators, and the sensor array typically utilizes hydrophones or other transducers. One or more seismic lines in the same geographic area define a survey, and a collection of one or more related surveys typically define an exploration prospect.
As the seismic source array passes over the exploration prospect, the source waves travel downward through the sea floor and the subsurface formations. Portions of the seismic wave energy are reflected back into the water by the sea floor and by interfaces between subsurface rock layers. The returning reflected waves generate pressure pulses, and the sensor array generates output signals representing such pressure pulses. The output signals are recorded on tapes and can be processed to identify certain relationships. For example, the propagation time of a seismic wave from a reflection point is proportional to the depth of the reflection point, and the processed output signals can be merged with position data to generate topographical representations of the subsurface formations.
Marine seismic data acquisition collects vast quantities of seismic and positioning data, and such data represents numerous parameters having multiple error sources. Wind, waves, and currents physically move the seismic streamers relative to the tow vessel in a "feathering angle" relative to the tow vessel heading. A relatively small feathering angle of five percent may offset a streamer point hundreds of meters from the survey line. Errors also occur due to the dispersal of the subsurface wave path reflection points, the occurrence of source and receiver offsets, the inclination of the reflecting surfaces, and because of other factors. The accuracy and usefulness of seismic data requires that multiple data processing procedures accurately locate the data points representing the seismic data.
Various data gathering systems collect and process seismic data. In U.S. Pat. No. 4,787,069 to Beauducel et al. (1988), electronic modules filtered and amplified signals near each seismic receiver, and an acquisition apparatus digitized, stored and multiplexed signals from the seismic receivers to a ship-based central control and recording device.
U.S. Pat. No. 4,635,237 to Benestad et al. (1987) disclosed a system for transmitting information between seismic data acquisition devices and a central receiver. Benestad et al. described how conventional seismic data acquisition systems have multiple electrical contacts and connectors which increase the probability of faults. Arbitrary faults due to an electronic malfunction were identified by a data selector which screened data before the data was entered into the data stream. An extra data transmission line was included for transmitting a data stream following a line break or short-circuit in one of the ordinary transmission lines, and a signal indicating the error was sent to a central control unit.
U.S. Pat. No. 4,561,073 to Aeter et al. (1985) disclosed a system for sorting seismic data in a marine survey by sorting the data into defined squares, and by evaluating the measurement results for each square. By categorizing the data into geographic squares, errors and deviations caused by wind and other conditions was evaluated before the entire data set was processed. If sufficient data for such geographic space was not received, additional seismic data for such geographic space could be acquired.
In U.S. Pat. No. 4,663,743 to Rampuria et al. (1987), a data transcriber system received data in a first medium and outputted the data in a second medium. The transcriber system permitted detection and correction of data errors. However, the system required significant operator intervention to set processing parameters, to choose transcription types and input modes, to view input parameters, to modify data, and to output the data.
In U.S. Pat. No. 4,759,636 to Ahern et al. (1988), surrogate seismic signals were produced from multiple selected channels on a real time basis to represent the detected seismic data. These surrogate signals were generated by sampling the multiplexed seismic signal at selected time intervals. The surrogate signals consolidated the data quantities transmitted to a central processor for processing and interpretation. The surrogate signals were further used to evaluate the data quality control and to evaluate and optimize data acquisition parameters.
U.S. Pat. No. 4,682,307 to Newman (1987) also sought to provide a real-time data processing system by reducing the processed data. A single seismic source and a single receiver produced single trace data for processing, thereby reducing the total volume of data processed.
The emergence of 3-D data seismic processing as a geophysical tool and of multiple, large streamer arrays towed behind seismic vessels results in additional data available for processing. Known processing systems that selectively sampled the data sets ignore much of the available data. Moreover, known processing systems do not provide comprehensive real-time processing and quality control capabilities for maintaining the integrity of the processed data. Accordingly, a need exists for an improved system that enhances contemporaneous processing capabilities and provides real-time and near real-time quality control over the source data and processed results.